A Tribute to the Earthen Dam

...A mini lesson in hydrology by Emily and Nena
Scroll down for sweet movies!!!

I apologize in advance: This is not a post about kayaking... It is, however, related to the outdoors and water.

Along the top of the earthen dam.

Last fall I took a really interesting class called "Watershed Engineering," in which we analyzed and designed water control structures (dams, culverts, channels, etc). One of our projects was to analyze the Virgil Creek earthen dam.  For some unknown reason, a few of us fell in love with the dam, and have been back to visit (and camp out...) a few times.
 

Looking upstream, from the top of the dam. This is a typical flow for the creek.

The dam is a "dry dam", which means it only holds back water when there is a large rainfall event.  It was designed after a storm in 1981 that cause massive flooding in the town of Dryden. Construction was completed in 1998. It was made to handle a 100-year flood, which means it can hold a LOT of water. The metal gates keep the gradient of the stream from being too steep, slowing down the water and preventing excess erosion. Today there was so much water that we couldn't even see these gates!

The emergency spillway

Around the outside there's also an "emergency spillway" (see above) which would hypothetically route extra water around the dam, should the flood be greater than a 100 year flood. If water over-tops an earthen dam, the dirt will erode quickly, and the entire dam will disintegrate in minutes, causing an incredibly destructive wave to go down and upstream from the site. Ok, enough background. Today Emily and I (we missed our other watershed engineering friends who have moved on from Ithaca!) went to the dam to see what happened after 5 inches of rain fell in one day. We didn't know what to expect. There was a LOT of water!

Fall 2009 - normal fall day!

Fall 2010 - after a big storm on Sept 29th!

It was really exciting for water nerds like me and Emily! There are so many things we wanted to tell you, so we decided to make a mini movie about it. I hope I don't normally say 'like' this often...

This one is only about 1 minute long and shows the outflow of the dam. It's crazy! Normally there is just a calm trickle of water... This movie shows you the energy dissipator in full force -- it forces the water to churn intensely and get rid of some of its energy so it won't scourge the sides of the creek and cause massive erosion.

 

Ok, I'm officially a huge nerd. Back to kayaking now. Post about circumnavigating Otisco Lake will arrive shortly after Sunday!